Researcher Frank Nijsen has been appointed Professor of Local Radionuclide Interventions at Radboudumc / Radboud University. Through his research, he develops therapies that irradiate difficult-to-treat tumors from the inside. His group works with innovative techniques such as radioactive microspheres and gels, image-guided robot and needle placement, and precise delivery of radioactive substances directly into tumors. This offers particular promise for tumors that are hard to treat, such as those in the liver, pancreas, and brain: the tumor is irradiated from within while healthy tissue is largely spared.
One of the techniques Frank Nijsen is developing is Dose Painting: ‘painting’ a tumor with a lethal radiation dose. The aim is to treat the entire tumor while sparing as much healthy tissue as possible. ‘It resembles the paint-by-numbers kits we did as children’, he says. The technique uses a smart, image-guided needle that is inserted through the skin and guided to the tumor under CT or MRI imaging. Together with TU Delft, an innovative needle system has been developed. Through rotation, depth control, and extension, the needle can reach almost the entire tumor, after which a high local radiation dose is administered.
Robots at work
However, this innovative technique encountered a major obstacle: for larger and hard-to-reach tumors, the number of required needle positions and the required precision can be challenging. Therefore, together with the University of Twente, Nijsen is developing a robotic system that can guide the needle through the tumor faster and more accurately and deliver extremely small amounts of radioactivity with precision. ‘The combination of imaging, artificial intelligence, and robotics makes it possible to irradiate hard-to-treat tumors more effectively’, he explains. ‘This is not only a technological advancement and an improvement in treatment, but also a response to the growing healthcare demand and the increasing shortage of healthcare professionals.’
From veterinary medicine to clinic
Before Nijsen’s technology can be widely applied in clinical practice, additional training and research are required. That step is already being taken in veterinary medicine, where the technique is being tested in practice on dogs and cats with tumors. Together with a team of veterinarians from Utrecht University’s Faculty of Veterinary Medicine, the treatment is being carried out carefully. More than fifty animals have already been treated. ‘Many lived longer as a result, and some have even been completely cured’, says Nijsen. Building on these results, treatments for pancreatic tumors in human patients have been initiated. In the near future, robotic delivery will be used at Radboudumc for the first time as a next step toward application in both animals and humans.
Radioembolization
Another technique that Nijsen and his group have been working on for years is image-guided radioembolization. Radioactive microspheres are delivered via a catheter close to liver tumors. The microspheres become lodged in the tumor’s blood vessels and irradiate it from within. Worldwide, this treatment is often still performed without direct imaging guidance. Doctors take scans beforehand, but real-time visualization during delivery was long not possible. Nijsen changed this with holmium microspheres—radioactive particles visible on MRI. Thanks to continuous monitoring, his team was able to work more safely and increase the tumor dose by up to a factor of three. As a result, some patients who had no remaining treatment options unexpectedly became eligible for curative treatment.
Immune system
During radioembolization, Nijsen sometimes observes untreated tumors elsewhere in the liver shrinking. This suggests that the treatment may activate the immune system. This effect is now being studied further, with the aim of making it reproducible. Treated patients are being closely analyzed to understand where and when radiation triggers the immune response.
Future of local radionuclide therapy
Nijsen is optimistic about the future of radionuclide therapy. ‘Over the next ten years, these treatments will be used more and more frequently. For various forms of chemotherapy, radioactive alternatives with fewer side effects are being developed. Some radiopharmaceuticals specifically target tumors. Other treatments, such as radioactive microspheres or gels, are delivered directly into the tumor. Both forms of therapy will play an important role in cancer care in the coming years.’
For this reason, Nijsen is working with a large team on a Theragnostic Center: a safe innovation environment where new radioactive treatments can be rapidly developed, tested, and made available to patients in the Netherlands and beyond.
Career
Frank Nijsen studied Biology and Medical Biology at the University of Amsterdam. In 2001, he obtained his PhD at Utrecht University with research on radioactive holmium microspheres for the treatment of liver tumors. Based on this work, he co-founded the spin-off company Quirem Medical in 2013, which made holmium microspheres available to liver cancer patients in Europe. In 2020, the company was acquired by the Japanese firm Terumo. Since 2017, he has been principal investigator in Image-Guided Local Nuclear Interventions at Radboudumc, and since 2024 he has also led the Minimally Invasive Image-Guided Intervention Center (MAGIC). His appointment as professor and research leader takes effect on 15 July 2026 for a period of five years.
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